Num Decodings

Author: hyejjun

decode-ways/hyejjun.js

@@ -0,0 +1,42 @@
+/**
+ * @param {string} s
+ * @return {number}
+ */
+
+var numDecodings = function (s) {
+    if (s == null || s.length === 0) {
+        return 0;
+    }
+
+    const n = s.length;
+    const dp = new Array(n + 1).fill(0);
+    dp[0] = 1;
+    dp[1] = s[0] === '0' ? 0 : 1;
+
+    for (let i = 2; i <= n; i++) {
+        const oneDigit = parseInt(s.substring(i - 1, i));
+        const twoDigits = parseInt(s.substring(i - 2, i));
+
+        // Check if single digit decoding is possible
+        if (oneDigit >= 1 && oneDigit <= 9) {
+            dp[i] += dp[i - 1];
+        }
+
+        // Check if two digit decoding is possible
+        if (twoDigits >= 10 && twoDigits <= 26) {
+            dp[i] += dp[i - 2];
+        }
+    }
+
+    return dp[n];
+};
+
+
+console.log(numDecodings("12"));
+console.log(numDecodings("226"));
+console.log(numDecodings("06"));
+
+/*
+시간 복잡도: O(n)
+공간 복잡도: O(n)
+*/